The influence of polyurethane precursor density on the electrochemical performance of supercapacitor composed of activated porous carbon

In this work, we studied the relationship between the electrochemical performance, the specific gravimetric capacitance, and the specific volumetric capacitance as the density of the polyurethane-derived porous carbon (PPC) was varied by adjusting the amount of water used during KOH activation-carbonization synthesis process. We characterized PPCs made using five different mass ratios of water to precursor (X) of 0.4, 0.5, 0.6, 0.7, and 0.8 and found that X of 0.6 (PPC-0.6) gave the most developed porous structure and the right amount of N and O heteroatoms. As the X increased from 0.4 to 0.8, the precursor density decreased. Among the five PPCs synthesized, PPC-0.6 showed the highest specific gravimetric capacitance of 458.2 F g−1 at a current density of 1 A g−1 in a 1 M H2SO4 electrolyte. Notably, a two-electrode SC device based on PPC-0.6 operated in a 1 M H2SO4 electrolyte could generate the highest energy density of 13.12 Wh kg−1 at a corresponding power density of 50 W kg−1 and maintain 97.55 % of its initial capacitance at the end of 10,000 cycles. The highest specific volumetric and gravimetric capacitances were 242.8 F cm−3 and 458.2 F g−1, respectively, achieved by PPC-0.8 and PPC-0.6. This study serves as a guide that demonstrates how the bulk density of porous carbon supercapacitor electrodes can be adjusted by changing the polymer precursor density, whereby the trade-off relationship was observed between the specific gravimetric capacitance and the specific volumetric capacitance.